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In Situ Visualization of Axon Growth and Growth Cone Dynamics in Acute Ex Vivo Embryonic Brain Slice Cultures
Published on: October 14, 2021
Life among the axons
1Department of Physiology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA. carmstro@mail.med.upenn.edu
Annual Review of Physiology
|October 21, 2006
Summary
This chapter details the evolution of understanding electrical signaling, from early experiments to the concept of gated ion channels. It highlights the transformation of abstract electrical conductances into tangible biological mechanisms.
Area of Science:
- Biophysics
- Neuroscience
- Cellular Electrophysiology
Background:
- The discovery of electricity's role in biological systems.
- The foundational work of Hodgkin & Huxley on electrical signaling in 1952.
- The historical progression from basic electrical principles to complex biological functions.
Observation:
- Early experiments like Galvani's frog legs and Volta's batteries laid groundwork.
- The pervasive influence of electricity in both plant and animal life became evident.
- Hodgkin & Huxley's model described electrical signaling using abstract conductances.
Findings:
- This work traces the conceptual shift from abstract electrical conductances.
- It details the emergence of the more concrete concept of gated ion channels.
- The chapter provides a personal perspective on this scientific evolution.
Implications:
- Understanding gated ion channels is crucial for modern biology and medicine.
- This knowledge underpins advancements in neuroscience, pharmacology, and bioengineering.
- The evolution of this concept illustrates the dynamic nature of scientific discovery.
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Neurons: The Axon
Axons are long, cytoplasmic processes of nerve cells capable of propagating electrical impulses known as action potentials. The cytoplasm or axoplasm of an axon contains neurofibrils, neurotubules, small vesicles, lysosomes, mitochondria, and various enzymes, all encased within the axolemma, the plasma membrane of the axon.
The axon attaches to the cell body at a cone-shaped elevation called the axon hillock. The initial part of the axon, closest to the hillock, is known as the initial segment.
The axon attaches to the cell body at a cone-shaped elevation called the axon hillock. The initial part of the axon, closest to the hillock, is known as the initial segment.
Action Potentials
Overview
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Neurons communicate by firing action potentials—the electrochemical signal that is propagated along the axon. The signal results in the release of neurotransmitters at axon terminals, thereby transmitting information to the nervous system. An action potential is a specific "all-or-none" change in membrane potential that results in a rapid spike in voltage.
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Neurons communicate by firing action potentials—the electrochemical signal that is propagated along the axon. The signal results in the release of neurotransmitters at axon terminals, thereby transmitting information to the nervous system. An action potential is a specific "all-or-none" change in membrane potential that results in a rapid spike in voltage.
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The myelin sheath is a multilayered lipid and protein covering that insulates the axon of a neuron, enhancing the speed of nerve impulse conduction. Axons without this sheath are referred to as unmyelinated. Two types of neuroglia, Schwann cells in the peripheral nervous system (PNS) and oligodendrocytes in the central nervous system (CNS) are responsible for producing myelin sheaths.
Schwann cells begin to form myelin sheaths around axons during fetal development. They wrap around a small...
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Neurons are the main type of cell in the nervous system that generate and transmit electrochemical signals. They primarily communicate with each other using neurotransmitters at specific junctions called synapses. Neurons come in many shapes that often relate to their function, but most share three main structures: an axon and dendrites that extend out from a cell body.
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The neuronal cell body—the soma— houses the nucleus and organelles vital to cellular...
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